Method of manufacturing magnetic recording medium and the magnetic recording medium

ABSTRACT

A method of manufacturing a magnetic recording medium which includes a bonding sub-layer substantially and forms a lubricant layer having a width. A method of manufacturing a magnetic recording medium includes the steps of: a) laminating an underlayer, a magnetic layer for recording, and a protection layer of amorphous carbon on a substrate of the magnetic layer for recording medium in turn, and b) repeating a process to the protection layer of amorphous carbon comprising an application process of applying a lubricant, a subsequent ultraviolet rays treatment process, and a subsequent washing process for removing the lubricant which is not connected to the protection layer of amorphous carbon, the process being repeated plural times.

This is a continuation of International application No. PCT/JP99/03363,filed Jun. 24,1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a recordingmedium and the recording medium for use in a magnetic recording andreproduction device such as a hard disk drives serving as a secondarystorage device of computers.

2. Description of the Related Art

In recent years, there has been an increasing need for high-densityrecording in magnetic storage devices such as hard disk drives. In suchhard disk drives for high-density recording, it is necessary to reducethe magnetic spacing, which is a space formed between a magnetic headprovided in the magnetic disk drives and the surface of a magnetic diskserving as a recording medium in the main body of the hard disk drives,as much as possible. In other words, the gap between the magnetic headand the magnetic disk surface, scanned by the magnetic head, should beas small as possible.

FIG. 1 is a schematic diagram showing a magnetic disk drive 100including a magnetic head 120 and a rotatable magnetic disk 110 of therelated art. FIG. 1 is illustrated in an enlarged view; so as to clearlyshow the layered structure of the magnetic disk 110 and magnetic springS.

Referring to FIG. 1, the magnetic disk has a multilayered structureincluding a substrate 111, an underlayer 113 formed on the substrate111, and a magnetic layer 115 formed on the underlayer 113. A protectionlayer 117 of amorphous carbon is provided on the magnetic layer 115.

The magnetic disk drive 100 described above generally operates inaccordance with the so-called contact-start-stop (CSS) mode. With theCSS mode, a lift surface 120 a of the magnetic head 120 contacts andslides over the surface of the magnetic disk 110 at the start or stopphase of rotation of the magnetic disk 110. The magnetic disk 110 has aCSS area within its surface. The magnetic head 120 contacts the CSS areawhen the magnetic disk 110 starts and stops rotating. On the other hand,the magnetic head 120 can float in the air with airflow caused by therotation of the magnetic disk 110 when the magnetic disk drive 100operates.

However, even during steady state operation, the magnetic head 120 maycome into contact with the surface of the magnetic disk 110 due tounexpected affairs. To accommodate the continuous contact between thehead 120 and the disk 110 when the drive starts or stops and theintermittent contact between the head 120 and the disk 110 when the headcollides with unexpected affairs, the surface of the magnetic disk 110should have both a low coefficient of friction and a high resistance toabrasion.

The magnetic disk 110 has a lubrication layer 119, which is formed bylubricant, on the protection layer 117. As the lubricant layer 119 hasinfluence on the friction and the abrasion properties of the magneticdisk 110, it is important to keep the lubrication layer 119 in goodconditions for maintaining the reliability of the magnetic disk drive100.

In the near future, still lower spacing between the magnetic head 120and the surface of the magnetic disk 110 will be required forhigh-density recording. Thus, it is really important to keep the surfaceof the magnetic disk 110 with a low coefficient of friction, a highresistance to abrasion and water repellency over a longer period oftime.

However, the inside of the magnetic disk drive 100 reaches a hightemperature. Furthermore, the magnetic disk 110 rotates at high speed inthe drive 100. Even under the most benign ambient conditions, theinterior of the disk drive 100 is a high-temperature environment due tothe high rate of rotation of the disk 110 relative to the head 120.Increasing the rate of rotation of the disk 110 increases thecentrifugal force that acts on any element of the lubrication layer 119;increasing the temperature of the disk 110 also increases the mobilityof the elements of the lubrication layer 119. Elements of thelubrication layer 119 thus tend to move towards the circumference of thedisk 110 over time, where they are more likely to be spun off the disk110, so that the lubrication layer 119 tends to become thinner as theservice time of the disk increases. A thinning lubrication layer 119loses the capability of fulfilling its several roles. In order toprevent the lubrication layer 119 from losing the capability, thelubrication layer 119 should be formed by lubricant having strongadsorptive property to the surface (the protection layer 117) of themagnetic disk 110.

Concerning the lubrication layer 119 on the protection layer 117, it isconsidered that the lubrication layer 119 consists of a “bondingsub-layer” 119 a, which consists of molecules that bind strongly to theprotection layer 117, and a “mobile sub-layer” 119 b, which consists ofmolecules that bind weakly to the protection layer 117. The mobilesub-layer 119 b tends to undergo spin off as a result of centrifugalforce by the disk rotation. It is estimated as a main reason of thethinning of the lubrication layer 119 as described above that the mobilelayer 119 b tends to move to the circumferential part of the magneticdisk 110 and much mobile sub-layer 119 b breaks away from the magneticdisk 110 in the end.

It is important to maintain the original thickness of the lubricationlayer 119 as much as possible, even for the magnetic disk 110 that isused for a long period of time. Thinning of the lubrication layer 119 isassociated with loss of the mobile sub-layer 119 b. Minimizing thethinning of the lubrication layer is accomplished by maximizing the“bonding ratio” of the lubrication layer, which is the ratio of thebonding sub-layer 119 a to the mobile sub-layer 119 b.

Many prior arts disks attempted to increase the thickness of the bondingsub-layer 119 a. In the prior arts, a lubricant is applied to theprotection layer 117 of the magnetic disk 110, and ultraviolet rayscuring treatment or heating treatment is implemented on the lubricationlayer 119 (lubricant) for increasing the ratio of the bonding sub-layer119 a (the bonding ratio).

However, it is not enough for increasing the bonding ratio to implementthe above treatment only one time.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention is toprovide a novel and useful method of manufacturing a magnetic recordingmedium in which the problems described above are eliminated. Anotherobject of the present invention is to provide a magnetic mediummanufactured by the method.

The above objects are accomplished by a method of manufacturing amagnetic recording medium including steps of: a) laminating anunderlayer, a magnetic layer for recording, and a protection layer ofamorphous carbon on a substrate of the magnetic recording medium inturn, and b) repeating a process to the protection layer of amorphouscarbon comprising an application process of applying a lubricant, asubsequent ultraviolet rays treatment process, and a subsequent washingprocess for removing the lubricant which is not connected to theprotection layer of amorphous carbon plural times.

The process to the protection layer of amorphous carbon comprising theapplication process of applying the lubricant, the subsequentultraviolet rays treatment process, and the subsequent washing processfor removing the lubricant which is not connected to the protectionlayer of amorphous carbon is repeated plural times. Thus, it is possibleto reduce the ratio of the mobile sub-layer and increase the ratio ofthe bonding sub-layer by repeating plural times one set of the abovethree processes.

That is, the combination power between a surface of the protection layerof amorphous carbon and the lubricant applied on the protection layer ofamorphous carbon will be strengthened. On the other hand, the bondingsub-layer whose combination power with the protection layer of amorphouscarbon is lower will be removed by the subsequent wash process. Underthe above state, it is easy to combine the lubricant with the surface ofthe protection layer of amorphous carbon because the lubricant isapplied again. It is possible to increase the bonding ratio by repeatingthe process.

It is possible to either keep respective conditions for the aboverespective processes the same and repeat the process or modify acondition. For instance, an irradiation time in the ultraviolet rays(UV) treatment process can be modified based on a forming state of thebonding sub-layer.

It is difficult to know exactly the ratio of the mobile sub-layer andthe bonding sub-layer in the lubrication layer formed on the protectionlayer of amorphous carbon. Accordingly, in the present invention, themagnetic recording medium on which the lubrication layer is formed iswashed well by designated solvent and the lubrication layer implementedthe wash process is regarded as the mobile sub-layer. Therefore, in thepresent invention, the increase of the bonding ratio means increase thewidth of the lubrication layer implemented the wash process.

It is preferred that the lubricant in the method is a compound of theperfluoro-polyether with an end-group including piperonyl or hydroxylgroup. The bonding ration can be increased precisely by applying thelubricant, which is a compound of the perfluoro-polyether with anend-group including piperonyl or hydroxyl group and implementingultraviolet rays (UV) treatment process as a process to strengthen thecombination with the protection layer of amorphous carbon.

As a liquid lubricant which is a compound that is a perfluoro-polyetherwith an end-group including piperonyl group, FOMBLIN AM2001 availablefrom Ausimont corp and others, more preferably FOMBLIN AM3001, isapplicable to be used. As a liquid lubricant which is a compound that'sa perfluoro-polyether with an end-group including hydroxyl group,FOMBLIN Zdo12000 available from Ausimont corp and others, morepreferably FOMBLIN AMZdo14000, is applicable to be used.

The above objects are also accomplished by a method of manufacturing amagnetic recording medium including the steps of: a) laminating anunderlayer, a magnetic layer for recording, and a protection layer ofamorphous carbon on a substrate of the magnetic recording medium inturn, and b) repeating a process to the protection layer of amorphouscarbon comprising an application process of applying a lubricant, ansubsequent heat treatment process, and a subsequent washing process forremoving the lubricant which is not connected to the protection layer ofamorphous carbon plural times.

It is possible to either keep respective conditions for the aboverespective processes the same and repeat the process or modify acondition. For instance, a temperature of heating in the heat treatmentprocess can be modified based on a forming state of the bondingsub-layer.

It is preferred that the lubricant in the above-described method is acompound of the perfluoro-polyether with an end-group including hydroxylgroup.

The bonding ration can be increased by applying the lubricant which is acompound of the perfluoro-polyether with an end-group including hydroxylgroup and implementing the heat treatment process as a process tostrengthen the combination with the protection layer of amorphouscarbon.

Furthermore, the above objects are also accomplished by a method ofmanufacturing a magnetic recording medium including the steps of: a)laminating an underlayer, a magnetic layer for recording, and aprotection layer of amorphous carbon on a substrate of the magneticrecording medium in turn, and b) repeating a process to the protectionlayer of amorphous carbon comprising an application process of applyinga lubricant, and a subsequent ultraviolet rays treatment process pluraltimes.

It is preferred that the lubricant in the method is a compound of theperfluoro-polyether with an end-group including piperonyl or hydroxylgroup.

Furthermore, the above objects are also accomplished by a method ofmanufacturing a magnetic recording medium including the steps of: a)laminating an underlayer, a magnetic layer for recording, and aprotection layer of amorphous carbon on a substrate of the magneticrecording medium in turn, and b) repeating a process to the protectionlayer of amorphous carbon comprising an application process of applyinga lubricant, and a subsequent heat treatment process plural times.

It is preferred that the lubricant in the method is a compound of theperfluoro-polyether with an end-group including hydroxyl group.

Other objects in the present invention are to provide a magneticrecording medium having a lubricant layer comprising a bonding sub-layeron a surface of the magnetic recording medium and manufactured by aprocess including the steps of a) laminating an underlayer, a magneticlayer for recording, and a protection layer of amorphous carbon on asubstrate of the magnetic recording medium in turn, and, b) repeatingplural times a process to the protection layer of amorphous carboncomprising an application process of applying a lubricant which is acompound of the perfluoro-polyether with an end-group includingpiperonyl or hydroxyl group, and a subsequent ultraviolet rays treatmentprocess, or b) repeating plural times a progress to the protection layerof amorphous carbon comprising an application process of applying alubricant which is a compound of the perfluoro-polyether with anend-group including piperonyl or hydroxyl group, a subsequentultraviolet rays treatment process, and a further subsequent washingprocess for removing the lubricant which is not connected to theprotection layer of amorphous carbon.

Still other objects in the present invention are to provide a magneticrecording medium having a lubricant layer including a bonding sub-layeron a surface of the magnetic recording medium and manufactured by aprocess including the steps of a) laminating an underlayer, a magneticlayer for recording, and a protection layer of amorphous carbon on asubstrate of the magnetic recording medium in turn, and, b) repeatingplural times a process to the protection layer of amorphous carboncomprising an application process of applying a lubricant which is acompound of the perfluoro-polyether with an end-group including hydroxylgroup, and a subsequent heat treatment process, or b) repeating pluraltimes a process to the protection layer of amorphous carbon comprisingan application process of applying a lubricant which is a compound ofthe perfluoro-polyether with an end-group including hydroxyl group, aheat treatment process, and a further subsequent washing process forremoving the lubricant which is not connected to the protection layer ofamorphous carbon.

Other objects and further of the present invention will be apparent fromthe following detailed description when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a relationship between a magnetichead and a rotating magnetic disk in the magnetic disk drive of thepresent invention.

FIG. 2 is a diagram showing a step of an application process of applyinga lubricant, an ultraviolet rays (UV) treatment process, and a washingprocess to the magnetic recording medium according to a first embodimentof the present invention.

FIG. 3 is a view showing a state that the bonding sub-layer isincreasing by repeating one set process of an application process ofapplying a lubricant, an ultraviolet rays (UV) treatment process, and awashing process plural times.

FIG. 4 is a diagram showing a step of the application process ofapplying a lubricant, a heat treatment process, and a washing process tothe magnetic recording medium.

FIG. 5 is a view showing a state that the bonding sub-layer isincreasing by repeating one set process of an application process ofapplying a lubricant, a heat treatment process, and a washing process,plural times.

FIG. 6A is a view showing a state that the bonding sub-layer isincreasing by repeating one set process of an application process ofapplying a lubricant (I) and an ultraviolet rays (UV) treatment process(II) with a compound of the perfluoro-polyether with an end-groupincluding piperonyl group as the lubricant; FIG. 6B is a view showing astate that the bonding sub-layer is increasing by repeating one setprocess of an application process of applying a lubricant (I) and anultraviolet rays (UV) treatment process (II) with a compound of theperfluoro-polyether with an end-group including hydroxyl group as thelubricant; and FIG. 6C is a view showing a state that the bondingsub-layer is increasing by repeating one set process of an applicationprocess of applying a lubricant (I) and a heat treatment process (II)with a compound of the perfluoro-polyether with an end-group includinghydroxyl group as the lubricant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be described, with reference to FIGS. 2 through 6, ofprinciples and embodiments of the present invention.

At first, a first embodiment of the present invention will be described.It is the first embodiment of the present invention to repeat pluraltimes one set process of an application process of applying a lubricant,an ultraviolet rays (UV) treatment process, and a washing process to aprotection layer of amorphous carbon on a magnetic recording medium.

FIG. 2 is a diagram showing a step of the to application process ofapplying a lubricant, an ultraviolet rays (UV) treatment process, and awashing process to the magnetic recording medium.

In the first embodiment of the present invention, a magnetic recordingmedium 1 manufactured by the prior art is prepared in advance. Themagnetic recording medium 1 3 has a multilayered structure including asubstrate, an underlayer formed on the substrate, and a magnetic layerformed on the underlayer. A protection layer of amorphous carbon isprovided on the magnetic layer. The above-mentioned multilayeredstructure is the same as the prior arts shown in FIG. 1.

As FIG. 2 shows, in the present invention, at first the magneticrecording medium 1 is immersed in a bath of a liquid lubricant 4 filledin a container 40 and an application process (I) is implemented by a dipmethod for example. By the above process, the liquid lubricant 4 isapplied on the protection layer of amorphous carbon which is a highestlayer of the magnetic recording medium 1, so that a desirablelubrication layer 2 is formed.

The liquid lubricant 4 is preferably a compound that is aperfluoro-polyether with an end-group including piperonyl group. Thelubricant 4 may be a compound such as FOMBLIN AM3001 available fromAusimont corp. The liquid lubricant 4 is prepared by diluting theFOMBLIN AM3001 to roughly 0.05 wt % in fluorocarbon solvent such asFLORINATE FC-77 of Sumitomo 3M corp. The application process (I) by thedip method is implemented for 30 seconds as a dipped time and pullingthe magnetic recording medium 1 from the bath at 2.3 mm per second forinstance. The useful dipping method may not be limited, a known methodsuch as spin-coating method and wiping method are available too.

Next, as FIG. 2 shows, a ultraviolet rays (UV) treatment process (II) isimplemented to the lubrication layer 2 formed on the magnetic recordingmedium 1. By this process, it is possible to strengthen a combinationpower between the lubrication layer 2 and the protection layer ofamorphous carbon. That is, it is possible to accelerate a change from amobile sub-layer to a bonding sub-layer in the lubrication layer 2 andincrease a bonding ratio.

In the ultraviolet rays (UV) treatment process (II), the UV wavelengthof about 200 nm and under is irradiated to the lubrication layer 2, andthe duration may be set to roughly 60 seconds. It is possible to combinetwo or more kinds of ultraviolet rays, whose wavelengths are about 254nm and 185 nm for instance.

In FIG. 2. A shown in the light side of the container 40 roughlyschematically shows a construction of the lubrication layer 2 on themagnetic recording medium 1. Thus, there are a lot of mobile sub-layers22 whose combination power is weak, as well as the bonding sub-layer 21strongly combining with the protection layer of amorphous carbon in thelubrication layer 2 formed on the magnetic recording medium 1, after theapplication process of applying the lubricant 4 but before theultraviolet rays (UV) treatment process. It is possible to change fromthe mobile sub-layers to the bonding sub-layer by implementing theultraviolet rays (UV) treatment process to the lubrication layer 2.However, the mobile sub-layer is still contained in the lubricationlayer after an ultraviolet rays (UV) treatment process.

In order to solve the above state, a wash treatment (III) is implementedby immersing the magnetic recording medium 1 in a bath of a solvent 6for washing filled in a container 60, in the present embodiment. Themobile sub-layer 22 whose combination power with the protection layer ofamorphous carbon is weak will be removed from the surface of themagnetic recording medium 1 by the wash process. Accordingly, it ispossible to manufacture the magnetic recording medium 1 formed on itssurface by the lubrication layer 2 comprised of only the bondingsub-layer 21 substantially, as B in the light side of the container 60in FIG. 2 roughly schematically shows.

The fluorocarbon solvent that is the same as for diluting the abovelubricant can be used as the solvent 6 for washing in this embodiment.The useful fluorocarbon solvent may not be limited, and other solvent isavailable as long as it can remove the mobile sub-layer 22 from thesurface of the magnetic recording medium 1. The wash process (III) isimplemented for 30 seconds as a dipped time and by pulling the magneticrecording medium 1 from the bath at 2.3 mm per second for instance.

Furthermore, it can be accelerated to remove the mobile sub-layer 22from the surface of the magnetic recording medium 1 if the temperatureof solvent 6 for washing is roughly less than the boiling point (atabout 25 centigrade in case of FLORINATE FC-77), and if the magneticrecording medium 1 is washed by an ultrasonic generator in the washprocess (III).

In the present embodiment, one set process of an application process ofapplying the lubricant (I), the ultraviolet rays (UV) treatment process(II), and the washing process (III) is repeated plural times. It ispossible that the magnetic recording medium 1 has a designated width andto manufacture the magnetic recording medium 1 formed on its surface bya lubrication layer 2 (C1) comprised of only the bonding sub-layer 21substantially, because the above process is repeated plural times. Incase that the above process is repeated plural times, for instance fivetimes, a lubrication layer 2 (C2) may be manufactured by omitting thelast process, for instance the five times wash process (III). It ispossible to either keep respective conditions for the above respectiveprocesses same and repeat the process or modify a condition. Forinstance, an irradiation time in the ultraviolet rays (UV) treatmentprocess (II) can be modified based on a forming state of the bondingsub-layer.

FIG. 3 is a view showing a state that the bonding sub-layer isincreasing by repeating one set process of an application process ofapplying a lubricant (I), an ultraviolet rays (UV) treatment process(II), and a washing process (III) plural times. FIG. 3 shows widths oflubricant layer (widths of the bonding sub-layer substantially) measuredafter the surface of the magnetic recording medium is washed by thesolvent for washing. The wash process is implemented for 30 seconds as adipped time and pulling the magnetic recording medium 1 from the bath offluorocarbon solvent at 2.3 mm per second for instance.

In FIG. 3 a white circle shows a case in which the application processand the ultraviolet rays (UV) treatment process are implemented one timeaccording to prior art. The width of the lubricant layer in this case isabout 1.25 nm.

The respective black circles show widths according to the presentinvention. That is, they show respective cases of that one set processof the application process of applying the lubricant (I), theultraviolet rays (UV) treatment process (II), and the washing process(III), repeated 2-6 times. The respective black circles clearly showthat the more the number of repeating the one set process increases, themore the width of the lubricant layer increases, about from 1.45 nm to1.75 nm.

Accordingly, according to the present invention, it is possible tomanufacture the magnetic recording medium having a desired width of thelubrication layer comprised of only the bonding sub-layer substantiallyby selecting the number of times for repeating the one set process ofthe application process of applying the lubricant (I), the ultravioletrays (UV) treatment process (II), and the washing process (III).

A similar effect as the above can be taken in the case where the liquidlubricant 4 that is a perfluoro-polyether with an end-group includinghydroxyl group is used in the first embodiment of the present invention.In this case, the lubricant 4 may be a compound such as FOMBLIN Zdo14000available from Ausimont corp. The liquid lubricant 4 is prepared bydiluting the FOMBLIN Zdo14000 to roughly 0.05 wt % in fluorocarbonsolvent such as FLORINATE FC-77 of Sumitomo 3M corp.

Next, a second embodiment of the present invention will be explainedbased on FIGS. 4 and 5. The second embodiment of the present inventionrepeats plural times one set process of an application process ofapplying a lubricant, a heat treatment process, and a washing process toa protection layer of amorphous carbon on a magnetic recording medium.As contrasted with the first embodiment in which the ultraviolet rays(UV) treatment process is implemented, the heat treatment process isimplemented in the second embodiment.

FIG. 4 is a diagram showing a step of the application process ofapplying a lubricant, a heat treatment process, and a washing process tothe magnetic recording medium. The same reference characters are appliedto like parts corresponding to the process in FIG. 2 showing the firstembodiment.

In the second embodiment of the present invention, a magnetic recordingmedium 1 manufactured by the prior art is prepared in advance as in thefirst embodiment. The magnetic recording medium 1 has a multilayeredstructure including a substrate, an underlayer formed on the substrate,and a magnetic layer formed on the underlayer. The protection layer ofamorphous carbon is provided on the magnetic layer.

In the second embodiment of the present invention, at first the magneticrecording medium 1 is immersed in a bath of a liquid lubricant 41 filledin a container 45 and an application process (I) is implemented by a dipmethod for example.

The liquid lubricant 41 is preferably a compound that is aperfluoro-polyether with an end-group including hydroxyl group. Thelubricant 41 may be a compound such as FOMBLIN Zdo14000 available fromAusimont corp. The liquid lubricant 41 is prepared by diluting theFOMBLIN Zdo14000 to roughly 0.05 wt % in fluorocarbon solvent such asFLORINATE FC-77 of Sumitomo 3M corp.

The application process (I) by the dip method is implemented for 30seconds as a dipped time, and by pulling the magnetic recording medium 1from the bath at 2.3 mm per second, for instance. The useful dippingmethod may not be limited, as known methods such as spin-coating methodand wiping method are available too.

Next, as FIG. 4 shows, a heat treatment process (II) is implemented tothe lubrication layer 2 formed on the magnetic recording medium 1. Bythis process, it is possible to strengthen a combination power betweenthe lubrication layer 2 and the protection layer of amorphous carbon.That is, it is possible to accelerate a change from a mobile sub-layerto a bonding sub-layer in the lubrication layer 2 and increase thebonding ratio.

A constant temperature container 70 is used in the heat treatmentprocess (II). The temperature inside of the constant temperaturecontainer 70 keeps at 100-120 centigrade. The magnetic recording medium1 on which the lubrication layer 2 is formed is heated by keeping forabout thirty minutes in the constant temperature container 70 in thesecond embodiment.

A wash treatment (III) is implemented by immersing the magneticrecording medium 1 in a bath of a solvent 6 for washing filled in acontainer 60. The conditions for the wash treatment in the presentembodiment are the same as in the first embodiment. It is possible tomanufacture the magnetic recording medium 1 formed on its surface by thelubrication layer 2 comprised of only the bonding sub-layer 21substantially according to the present embodiment.

In the present embodiment, one set process of an application process ofapplying the lubricant (I), the heat process (II), and the washingprocess (III) is repeated plural times. It is possible that the magneticrecording medium 1 has designated width and to manufacture the magneticrecording medium 1 formed on its surface by a lubrication layer 2 (C1)comprised of only the bonding sub-layer 21 substantially, because theabove process is repeated plural times. In case that the above processis repeated plural times, for instance five times, a lubrication layer 2(C2) may be manufactured by omitting the last process, for instance thefive times wash process (III). It is possible to either keep respectiveconditions for the above respective process same and repeat theprocesses or modify a condition, a temperature for heat process (II) forinstance, based on a forming state of the bonding sub-layer.

FIG. 5 is a view showing a state that the bonding sub-layer isincreasing by repeating one set process of an application process ofapplying a lubricant (I), the heat treatment process (II), and a washingprocess (III) plural times. FIG. 5 shows widths of lubricant layer(widths of the bonding sub-layer substantially) measured after thesurface of the magnetic recording medium is washed by the solvent forwashing as well as in FIG. 3.

In FIG. 5 a white circle shows a case in which the application processand the heat treatment process are implemented one time according toprior art. The width of lubricant layer in this case is about 0.85 nm.

The respective black circles show widths formed by a process of thepresent invention. That is, they show respective cases of the one setprocess of the application process of applying the lubricant (I), theultraviolet rays (UV) treatment process (II), and the washing process(III) being repeated 2 or 3 times. The respective black circles clearlyshow that the more the number of times repeating the one set processincreases, the more the width of the lubricant layer increases aboutfrom 1.05 nm to 1.15 nm. That is, the more the number of repetitions theone set process increases, the more the width of the lubricant layerincreases.

Further, other embodiments of the present invention will be explainedbased on FIG. 6.

Undermentioned embodiments are cases to manufacture the magneticrecording medium without implementing the wash treatment (III)implemented in the first and second embodiments.

That is, one embodiment is to repeat plural times one set process of anapplication process of applying a lubricant and an ultraviolet rays (UV)treatment process, and the other one is to repeat plural times one setprocess of an application process of applying a lubricant and a heattreatment process.

In the case of repeating plural times one set process of an applicationprocess of applying a lubricant and an ultraviolet rays (UV) treatmentprocess, the wash treatment process (III) as in the first embodiment ofthe present invention is not implemented and the magnetic recordingmedium 1 is manufactured with the same conditions as ones in the firstembodiment. Therefore, an explanation based on a figure showing processsteps is omitted.

In the case of repeating plural times one set process of applicationprocess of applying a lubricant and a heat treatment process, the washtreatment process (III) as in the second embodiment of the presentinvention is not implemented and the magnetic recording medium 1 ismanufactured with the same conditions as ones in the second embodiment.Therefore, an explanation based on a figure showing process steps isomitted.

Inventors of the present invention confirmed that it is possible toincrease the width of the bonding sub-layer by repeating one set processof the application process of applying the lubricant (I) and theultraviolet rays (UV) treatment process or heat process (II) pluraltimes without washing process (III).

FIG. 6 is a view showing a state that the bonding sub-layer isincreasing by the present embodiment which omits the wash treatmentprocess.

More particularly, FIG. 6A is a view showing a state that the bondingsub-layer is increasing by repeating one set process of an applicationprocess of applying a lubricant (I) and an ultraviolet rays (UV)treatment process (II) with a compound of the perfluoro-polyether withan end-group including piperonyl group as the lubricant; FIG. 6B is aview showing a state that the bonding sub-layer is increasing byrepeating one set process of an application process of applying alubricant (I) and an ultraviolet rays (UV) treatment process (II) with acompound of the perfluoro-polyether with an end-group including hydroxylgroup as the lubricant; and FIG. 6C is a view showing a state that thebonding sub-layer is increasing by repeating one set process of anapplication process of applying a lubricant (I) and a heat treatmentprocess (II) with a compound of the perfluoro-polyether with anend-group including hydroxyl group as the lubricant.

FIGS. 6A, 6B, and 6C show widths of lubricant layer (widths of thebonding sub-layer substantially) measured after the surface of themagnetic recording medium is washed by the solvent for washing.

In FIG. 6A a white circle shows a case in which the application processand the ultraviolet rays (UV) treatment process are implemented one timeaccording to the prior arts. The width of the lubricant layer in thiscase is about 1.3 nm.

The respective black circles show widths according to the presentinvention. That is, they show respective cases of the one set process ofthe application process of applying the lubricant (I) and theultraviolet rays (UV) treatment process (H) being repeated 2 or 3 times.The respective black circles clearly show that the more the number oftimes repeating the one set process increases, the more the width of thelubricant layer increases, about from 1.85 nm to 1.95 nm.

In FIG. 6B a white circle shows a case in which the application processand an ultraviolet rays (UV) treatment process are implemented one timeaccording to the prior arts. The width of the lubricant layer in thiscase is about 0.95 nm.

The respective black circles show widths according to the presentinvention. That is, they show respective cases of the one set process ofthe application process of applying the lubricant (I) and theultraviolet rays (UV) treatment process (11) being repeated 2 or 3times. The respective black circles clearly show that the more thenumber of times repeating the one set process increases, the more thewidth of the lubricant layer increases, about from 1.3 nm to 1.35 nm.

In FIG. 6C a white circle shows a case in which the application processand the heat treatment process are implemented one time according to theprior arts. The width of the lubricant layer in this case is about 0.95nm.

The respective black circles show widths according to the presentinvention. That is, they show respective cases of the one set process ofthe application process of applying the lubricant (I) and the heattreatment process (II) being repeated 2 or 3 times. The respective blackcircles clearly show that the more the number of times repeating the oneset process increases, the more the width of the lubricant layerincreases, about from 1.1 nm to 1.2 nm.

Therefore, it is possible to manufacture the magnetic recording medium 1forming the lubrication layer with high ratios of the bonding sub-layeron the protection layer of amorphous carbon by repeating one set ofapplication process of applying the lubricant and the ultraviolet rays(UV) treatment process or heat process.

In the meantime, there are states to use the compound of theperfluoro-polyether with an end-group including piperonyl or hydroxylgroup as the lubricant, to implement the ultraviolet rays (UV) treatmentprocess or heat process in order to increase ratios of the bondingsub-layer on the protection layer of amorphous carbon, to select thenumber of repeating the one set of the process if necessary, and to takeor omit the wash treatment process, in the present invention.Accordingly, the width of the lubrication layer formed on the magneticrecording medium manufactured by the present invention is not constant.

However, as FIGS. 3, 5, 6A, 6B, and 6C mentioning the widths of thelubricant layer (widths of the bonding sub-layer substantially) measuredafter the surface of the magnetic recording medium is washed by thesolvent for washing clearly show, it is possible to manufacture themagnetic recording medium forming the lubrication layer substantiallycomprised of at least 1 nm or more widths of the bonding sub-layer onthe protection layer of amorphous carbon, according to the presentinvention.

The present invention is not limited to these embodiments, but variousvariation and modifications may be made without departing from the scopeof the present invention.

It is possible to manufacture the magnetic recording medium forming thelubrication layer substantially comprised of at least 1 nm or morewidths of the bonding sub-layer on the protection layer of amorphouscarbon, according to the present invention. Furthermore, it is possibleto make a desired width by properly selecting the number of times thetreatment process is repeated.

Therefore, as compared with the lubricant layer of the magneticrecording medium in the prior art, the lubrication layer can bemaintained under a state of a low coefficient of friction for a longperiod of time, because the width of the magnetic recording mediumaccording to the present invention is thick and the reduction of thewidth of the lubrication layer is very little with time progress.

1. A method of manufacturing a magnetic recording medium comprising thesteps of: a) laminating an underlayer, a magnetic layer for recording,and a protection layer of amorphous carbon on a substrate of saidmagnetic recording medium in turn; and b) repeating a process to saidprotection layer of amorphous carbon plural times, said processcomprising an application process of applying a lubricant to saidprotection layer, a subsequent ultraviolet rays treatment process whichconnects a portion of said lubricant to said protection layer whileleaving a portion which is not connected to said protection layer, and asubsequent washing process which removes said lubricant which is notconnected to said protection layer by immersing the magnetic recordingmedium in a solvent.
 2. The method as claimed in claim 1, wherein saidlubricant is a compound of the perfluoro-polyether with an end-groupincluding piperonyl or hydroxyl group.
 3. The method as claimed in claim1 wherein said repeating a process to said protection layer of amorphouscarbon plural times increases a ratio of a thickness of said portion ofsaid lubricant connected to said protection layer to a thickness of aportion of said lubricant weakly connected to said protection layer. 4.A method of manufacturing a magnetic recording medium comprising thesteps of: a) laminating an underlayer, a magnetic layer for recording,and a protection layer of amorphous carbon on a substrate of saidmagnetic recording medium in turn; and b) repeating a process to saidprotection layer of amorphous carbon plural times, said processcomprising an application process of applying a lubricant to saidprotection layer, and a subsequent ultraviolet rays treatment processwhich connects a portion of said lubricant to said protection layer. 5.The method as claimed in claim 4, wherein said lubricant is a compoundof the perfluoro-polyether with an end-group including piperonyl orhydroxyl group.
 6. The method as claimed in claim 4 wherein saidrepeating a process to said protection layer of amorphous carbon pluraltimes increases a ratio of a thickness of said portion of said lubricantconnected to said protection layer to a thickness of a portion of saidlubricant weakly connected to said protection layer.